Method for fabricating semiconductor device

ABSTRACT

A semiconductor device includes a dielectric layer in which zirconium, hafnium, and a IV group element are mixed. A method for fabricating a capacitor includes forming a bottom electrode, forming the dielectric layer and forming a top electrode over the dielectric layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of Korean Patent Application No.10-2010-0126247, filed on Dec. 10, 2010, which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field

Exemplary embodiments of the present invention relate to a semiconductorfabrication technology, and more particularly, to a method for forming adielectric layer and a capacitor in a semiconductor device.

2. Description of the Related Art

As semiconductor memory devices become highly integrated, the area of aunit memory cell and an operating voltage thereof decreases. Here,despite the reduction in a memory cell area, capacitance of, forexample, 20 fF/cell or more is still desired to substantially preventthe occurrence of a soft error and a decrease in a refresh time.

To obtain an appropriate capacitance, a dielectric layer such asZrO₂/Al₂O₃/ZrO₂ is used. However, due to the integration, it isdifficult to ensure 20 fF/cell using the dielectric layer such asZrO₂/Al₂O₃/ZrO₂ unless an effective electrode area is increased byincreasing the height of a capacitor to above 1.7 μm in below 40nm-process DRAMs.

Here, it is desirable to obtain cell capacitance of 20 fF/cell or morefor below 40 nm-process DRAMs.

SUMMARY

An embodiment of the present invention is directed to a method forfabricating a semiconductor device including a dielectric layer forobtaining adequate cell capacitance.

In accordance with an embodiment of the present invention, asemiconductor device includes: a dielectric layer in which zirconium,hafnium, and a IV group element are mixed.

In accordance with another embodiment of the present invention, a methodfor fabricating a semiconductor device includes: forming a dielectriclayer in which zirconium, hafnium, and a IV group element are mixed.

In accordance with further another embodiment of the present invention,a method for fabricating a capacitor includes: forming a bottomelectrode; forming a dielectric layer over the bottom electrode, whereinzirconium, hafnium, and a IV group element are mixed in the dielectriclayer; and forming a top electrode over the dielectric layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are cross-sectional views illustrating the structure of adielectric layer according to an embodiment.

FIGS. 2A and 2B are timing diagrams illustrating an atomic layerdeposition method for forming a dielectric layer according to anembodiment.

FIGS. 3A to 3F are cross-sectional views illustrating a method forfabricating a capacitor according to an embodiment.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. Throughout the disclosure, like referencenumerals refer to like parts throughout the various figures andembodiments of the present invention.

The drawings are not necessarily to scale and in some instances,proportions may have been exaggerated in order to clearly illustratefeatures of the embodiments. When a first layer is referred to as being“on” a second layer or “on” a substrate, it not only refers to a casewhere the first layer is formed directly on the second layer or thesubstrate but also a case where a third layer exists between the firstlayer and the second layer or the substrate.

FIGS. 1A to 1C are cross-sectional views illustrating the structure of adielectric layer in accordance with an embodiment of the presentinvention. For illustration purposes, a IV group element is referred toas ‘M’, and a dielectric layer including a mixture of zirconium (Zr),hafnium (Hf), and a IV group element is referred to as a ‘ZrHfMO layer’.

Referring to FIG. 1A, a ZrHfMO layer 10 is formed. Since the M (that is,the IV group element) includes Si or Ce, the ZrHfMO layer 10 includes aZrHfSiO layer or a ZrHfCeO layer.

In obtaining a tetragonal phase and a cubic phase, a hafnium oxide layerHfO₂ thermodynamically has a phase change temperature of 1720° C. and2600° C. Meanwhile, if dopant is implanted, since dielectric tensorvalue is changed, a hexagonal phase or a cubic phase can be obtainednear 600° C.±100° C. through phase change. For example, if dopant withan ion radius smaller than that of the hafnium is implanted, thehexahedral phase can be obtained. If dopant with an ion radius largerthan that of the hafnium is implanted, the cubic phase can be obtained.

The ZrHfMO layer 10 is generated by mixing the hafnium oxide layer witha zirconium oxide layer ZrO₂ having physical/chemical properties similarto those of the hafnium oxide layer and relatively superior leakagecurrent restraining force due to a large energy band (energy band/Eg)value, and simultaneously introducing the IV group element thereto, sothat the hexagonal phase or the cubic phase is obtained near 600°C.±100° C. As a result, the ZrHfMO layer 10 has a dielectric constant of50 to 60 and an equivalent oxide thickness (Tax) of about 5 Å.

As described above, the ZrHfMO layer 10 having the dielectric constantof 50 to 60 and the equivalent oxide thickness (Tax) of about 5 Å isformed, so that adequate cell capacitance is obtained more easily.

Referring to FIG. 1B, an M-rich ZrHfMO layer 21 having a relatively highcomposition ratio of the IV group element is stacked on a ZrHfMO layer20. The total thickness of the dielectric layers 20 and 21 (that is, theZrHfMO layer 20 and the M-rich ZrHfMO layer 21) may be equal to or lessthan at least 100 Å, and the M-rich ZrHfMO is layer 21 is formed with athickness of 5 Å to 20 Å.

According to an example, the M-rich ZrHfMO layer 21 is stacked on theZrHfMO layer 20. However, the M-rich ZrHfMO layer 21 may be stackedunder the ZrHfMO layer 20.

Specifically, since the M-rich ZrHfMO layer 21 having the relativelyhigh composition ratio of the IV group element is formed to make contactwith an electrode, the leakage current restraining force may increase.

Referring to FIG. 1C, M-rich ZrHfMO layers 31A and 31B having arelatively high composition ratio of the IV group element are stacked onand under a ZrHfMO layer 30, respectively, so that a triple structure isobtained. The total thickness of the dielectric layers 30, 31A, and 31B(that is, the ZrHfMO layer 30 and the M-rich ZrHfMO layers 31A and 31B)may be equal to or less than 100 Å, and the M-rich ZrHfMO layers 31A and31B are formed with a thickness of 5 Å to 20 Å, respectively.

As described above, the ZrHfMO layer including a mixture of thezirconium, the hafnium and the IV group element has a nano-lamination ornano-mixed structure. More specifically, the ZrHfMO layer has astructure in which a very thin zirconium layer, a hafnium layer, and aIV group element layer are repeatedly stacked, wherein the zirconiumlayer, the hafnium layer, and the IV group element layer are each formednot to exceed the maximum mixable deposition thickness. As a result, theZrHfMO layer is provided in the form of a compound.

By using the ZrHfMO layer in the form of a compound, an equivalent oxidethickness (Tox) of 5 Å±0.5 Å with a dielectric constant of 50 to 60 maybe obtained. More specifically, the M-rich ZrHfMO layer having arelatively large IV group element is formed to make contact with anelectrode and a significant leakage current restraining force isobtained.

In order to form the ZrHfMO layer in the form of a compound, an atomiclayer deposition (ALD) method can be used, which will be described indetail with reference to FIGS. 2A and 2B.

FIGS. 2A and 2B are timing diagrams illustrating the ALD method forforming a dielectric layer according to the embodiment. In the presentembodiment, a nano-mix ALD method is used. For the nano-mix ALD method,processes substantially the same as those of the ALD method areperformed, where respective layers are repeatedly stacked with a verythin thickness and the respective layers are formed not to exceed themaximum mixable deposition thickness, so that a stack structure isprovided in the form of a compound.

As well known in the art, according to the ALD method, source gas issupplied, a source layer is created through chemically absorption on thesurface of a substrate, and remaining gas is purged using purge gas. Athin film is deposited when a reaction gas is introduced and reacts withthe source layer to deposit a desired atomic layer thin film, andremaining reaction gas is purged using the purge gas. The foregoingsteps constitute a unit cycle. The ALD method as described above uses asurface reaction mechanism, where a uniform, stable thin film isobtained. Here, the ALD method may be applied to a structure having alarge step difference and smaller design rules.

Furthermore, since the source gas and the reaction gas are sequentiallyintroduced and purged while separating them from each other, theoccurrence of particles due to a gas phase reaction may be reduced.

Referring to FIG. 2A, an ALD method for forming the ZrHfMO layer mayinclude a unit cycle for depositing a zirconium oxide layer ZrO₂, a unitcycle for depositing a hafnium oxide layer HfO₂, and a unit cycle fordepositing a IV group element oxide layer MO₂. Each unit cycle includesfour steps of source gas/purge/reaction gas/purge.

More specifically, the unit cycle for depositing the zirconium oxidelayer is performed in the sequence of a step 40A of introducingzirconium source gas, a step 41A of introducing purge gas, a step 42A ofintroducing reaction gas (for example, O₃), and a step 43A ofintroducing purge gas. The unit cycle for depositing the zirconium oxidelayer is repeated A times to form the zirconium oxide layer with adesired thickness, wherein the number A is adjusted not to exceed themaximum deposition thickness by which the zirconium oxide layer ismixable.

The unit cycle for depositing the hafnium oxide layer is performed inthe sequence of a step 40B of introducing hafnium source gas, a step 418of introducing purge gas, a step 42B of introducing reaction gas (forexample, O₃), and a step 43B of introducing purge gas. The unit cyclefor depositing the hafnium oxide layer is repeated B times to form thehafnium oxide layer with a desired thickness, wherein the number B isadjusted not to exceed the maximum deposition thickness of the hafniumoxide layer where the hafnium oxide layer remains mixable.

The unit cycle for depositing the IV group element oxide layer isperformed in the sequence of a step 40C of introducing IV group elementsource gas, a step 41C of introducing purge gas, a step 42C ofintroducing reaction gas (for example, O₃), and a step 43C ofintroducing purge gas. The unit cycle for depositing the IV groupelement oxide layer is repeated C times to form the IV group elementoxide layer with a desired thickness, wherein the number C is adjustednot to exceed the maximum deposition thickness where the IV groupelement oxide layer remains mixable.

The number of repetitions of each unit cycle may be changed according tothe type of a material, equipment and operating conditions, and adeposition speed or a growth speed may be changed according to thechemical composition of source gas or a precursor. A layer formed ineach unit cycle may not exceed the respective maximum mixable depositionthickness.

Here, the unit cycle for the zirconium oxide layer is repeated A times,the unit cycle for the hafnium oxide layer is repeated B times, the unitcycle for the IV group element oxide layer is repeated C times, and theentire cycle (all of the foregoing unit cycles) is repeated D times bythe number of desired stacks, so that the ZrHfMO layer having a mixedstructure is finally formed. Here, the A, B, C and D are naturalnumbers, each number of repetitions may be adjusted such that the totalthickness of dielectric layers does not exceed 100 Å and the content ofthe IV group element in the layer does not exceed 15% according to anexample.

Referring to FIG. 2B, an ALD method for forming the ZrHfMO layer mayinclude a unit cycle for depositing a zirconium hafnium oxide layerZrHfO and a unit cycle for depositing a IV group element oxide layerMO₂. Each unit cycle includes the following four subsequent steps:source gas/purge/reaction gas/purge.

According to an example, the unit cycle for depositing the zirconiumhafnium oxide layer is performed in the following sequence: a step 50Aof introducing mixed source gas of zirconium and hafnium, and a step 51Aof introducing purge gas, a step 52A of introducing reaction gas (forexample, O₃), and a step 53A of introducing purge gas. The unit cyclefor depositing the zirconium hafnium oxide layer is repeated E times toform the zirconium hafnium oxide layer with a desired thickness, whereinthe E is adjusted not to exceed the maximum deposition thickness wherethe zirconium hafnium oxide layer remains mixable.

The unit cycle for depositing the IV group element oxide layer isperformed in the following sequence: a step 50B of introducing IV groupelement source gas, a step 51B of introducing purge gas, a step 52B ofintroducing reaction gas (for example, O₃), and a step 53B ofintroducing purge gas. The unit cycle for depositing the IV groupelement oxide layer is repeated F times to form the IV group elementoxide layer with a desired thickness, wherein the F is adjusted not toexceed the maximum deposition thickness where the IV group element oxidelayer remains mixable.

The number of repetitions of each unit cycle may be changed according tothe type of a material, equipment and operating conditions, and adeposition speed or a growth speed may be changed according to thechemical composition of source gas or a precursor. A layer formed ineach unit cycle may not exceed the maximum mixable deposition thickness.

Furthermore, the unit cycle for the zirconium hafnium oxide layer isrepeated E times, the unit cycle for the IV group element oxide layer isrepeated F times, and the entire cycle is repeated G times to obtainedthe desired number of stacks, so that the ZrHfMO layer having a mixedstructure is finally formed. Here, the E, F and G are natural numbers,each number of repetitions may be adjusted such that the total thicknessof dielectric layers does not exceed 100 Å and the content of the IVgroup element in the layer does not exceed 15%, according to an example.

As described above, the ZrHfMO layer may be formed using the ALD methodillustrated in FIGS. 2A and 2B, and the unit cycle for the IV groupelement oxide layer may be adjusted to form the M-rich ZrHfMO layerillustrated in FIGS. 1B and 1C. While the M-rich ZrHfMO layer includesthe IV group element with a relatively large content, the number ofrepetitions of the cycle is adjusted such that the M-rich ZrHfMO layerhas a thickness of 5 Å to 20 Å.

FIGS. 3A to 3F are cross-sectional views illustrating a method forfabricating a capacitor according to the embodiment. In the embodiment,the capacitor may form any one of a flat plate, a concave structure, acylinder, and a pillar. Here, a concave-type capacitor is illustrated asan example.

Referring to FIG. 3A, an interlayer dielectric layer 61 is formed on asubstrate 60. The substrate 60 is a semiconductor substrate for which aDRAM process is to be performed and may be a substrate for which desiredprocesses for forming a gate pattern, a bit line pattern and the likehave been completed.

The interlayer dielectric layer 61 serves as interlayer dielectricbetween the substrate 60 and a top capacitor and may include an oxidelayer. The oxide layer may include one selected from the groupconsisting of a high density plasma (HDP) layer, a boron phosphorussilicate glass (BPSG) layer, a phosphorus silicate glass (PSG) layer, aboron silicate glass (BSG) layer, a tetra ethyle ortho silicate (TEOS)layer, a un-doped silicate glass (USG) layer, a fluorinated silicateglass (FSG) layer, a carbon doped oxide (CDO) layer, and an organosilicate glass (OSG) layer, or a stack layer of at least two layersthereof. Also, the oxide layer may include a layer coated using a spincoating method, such as a spin-on dielectric (SOD) layer.

A storage node contact plug 62 connected to the substrate 60 through theinterlayer dielectric layer 61 is formed. The storage node contact plug62 may be formed by etching the interlayer dielectric layer 61 to form acontact hole for exposing the substrate 60, filling a conductivematerial in the contact hole, and performing a planarization processuntil the surface of the interlayer dielectric layer 61 is exposed.

The conductive material may include one selected from the groupconsisting of a transition metal layer, a rare earth metal layer, analloy layer thereof, or a silicide layer thereof, or may include animpurity-doped polysilicon layer. Also, a stack structure in which atleast two layers of the conductive materials are stacked may be used.When the storage node contact plug 62 includes a metal layer (atransition metal, a rare earth metal), a barrier metal layer (notillustrated) may be further formed between the storage node contact plug62 and the contact hole. According to an example, polysilicon is used asthe conductive material.

An etch stop layer 63 is formed on the interlayer dielectric layer 61.The etch stop layer 63 substantially prevents the interlayer dielectriclayer 61 from being damaged when forming a contact hole for a subsequentbottom electrode and prevents a solution from penetrating into theinterlayer dielectric layer 61 in a dip-out process for forming acylinder-type capacitor. In this regard, while the etch stop layer 63includes a material having etching selectivity relative to theinterlayer dielectric layer 61 and a subsequent sacrificial layer, theetch stop layer 63 may include a nitride layer and the nitride layer mayinclude a silicon nitride layer (SiN, Si₃N₄).

A sacrificial layer 64 is formed on the etch stop layer 63. Thesacrificial layer 64 is for providing a contact hole for forming abottom electrode, and may include an oxide layer of a single layer or amultilayer. The oxide layer may include one selected from the groupconsisting of a high density plasma (HDP) layer, a boron phosphorussilicate glass (BPSG) layer, a phosphorus silicate glass (PSG) layer, aboron silicate glass (BSG) layer, a tetra ethyle ortho silicate (TEOS)layer, a un-doped silicate glass (USG) layer, a fluorinated silicateglass (FSG) layer, a carbon doped oxide (CDO) layer, and an organosilicate glass (OSG) layer, or a stack layer of at least two layersthereof. Also, the oxide layer may include a layer coated using a spincoating method, such as a spin-on dielectric (SOD) layer.

The sacrificial layer 64 and the etch stop layer 63 are etched to form astorage node hole 65 that exposes the storage node contact plug 62. Thestorage node hole 65 defines a region where the bottom electrode is tobe formed and may be formed by forming a mask pattern on the sacrificiallayer 64 and etching the sacrificial layer 64 and the etch stop layer 63using the mask pattern as an etch barrier. The mask pattern may beformed by coating a photoresist layer on the sacrificial layer 64 andpatterning the photoresist layer through an exposure and developmentprocess such that a region where a storage node hole is to be formed isopened. In order to ensure an etch margin insufficient when using thephotoresist layer, a hard mask layer may be additionally formed beforeforming the photoresist layer.

Referring to FIG. 3B, a bottom electrode 66 connected to the storagenode contact plug 62 through the sidewall and the bottom portion of thestorage node hole 65 is formed. The bottom electrode 66 includes a metalmaterial layer such as one selected from the group consisting of a TiNlayer, a TaN layer, a TiAlN layer, and a TaCN layer.

Although not illustrated in the drawing, a slightly plasma oxidationprocess may be performed on the surface of the bottom electrode 66 toform an interface layer thereon. The interface layer substantiallyprevents the occurrence of a leakage current by increasing a conductionbarrier height between the bottom electrode 66 and a subsequentdielectric layer.

Referring to FIG. 3C, a dielectric layer 67 including a mixture ofzirconium (Zr), hafnium (Hf), and IV group element is formed along astepped portion of a resultant structure including the bottom electrode66. The dielectric layer 67 may be formed using the ALD method, and isformed to have the structure illustrated in FIGS. 1A to 1C by performingthe ALD method illustrated in FIGS. 2A and 2B.

The dielectric layer 67 has a nano-lamination or a nano-mixed structureof the zirconium, the hafnium, and the IV group element and is providedin the form of a compound. The dielectric layer 67 provided in the formof a compound has an equivalent oxide thickness (Tox) of 5 Å±0.5 Å witha dielectric constant of 50 to 60. More specifically, the M-rich ZrHfMOlayer having a relatively large IV group element is formed to makecontact with an electrode and cause an increase in the leakage currentrestraining force.

Referring to FIG. 3D, a thermal process is performed with respect to thedielectric layer 67. The thermal process may include a primary thermalprocess for crystallization and a secondary thermal process for impurityelimination. Also, the thermal process may include a primary thermalprocess for crystallization and a plasma oxidation process for impurityelimination.

The primary thermal process induces crystallization to improve adielectric constant and is performed in a rapid thermal process (RTP) ora furnace at the temperature of 500° C. to 700° C. under the N₂atmosphere.

The secondary thermal process eliminates an impurity such as carbon or ahydrocarbon compound remaining in the dielectric layer 67 and eliminatesoxygen vacancy and may be performed in the rapid thermal process (RTP)or the furnace at atmospheric pressure or reduced pressure under the O₂or O₃ atmosphere.

Instead of the secondary thermal process, the plasma oxidation processmay be performed at the relatively low temperature of 300° C. to 500° C.under the pressure of 0.1 Torr to 10 Torr.

Referring to FIG. 3E, a plasma nitrification process is performed on thesurface of the dielectric layer 67. The plasma nitrification processenhances threshold electric field characteristics and improves thethermal stabilization in a subsequent thermal process and is performedusing remote N₂ plasma or NH₃ plasma at the temperature of 300° C. to500° C. under the pressure of 0.1 Torr to 10 Torr.

Referring to FIG. 3F, a top electrode 68 is formed on the dielectriclayer 67. The top electrode 68 may include a material substantially thesame as that of the bottom electrode 66. The top electrode 68, forexample, may be formed by depositing a metal-based electrode selectedfrom the group consisting of a TiN layer, a TaN layer, a TiAlN layer,and a TaCN layer.

Although not shown in the drawing, a capping layer or a buffer layer maybe stacked on the top electrode 68 in order to substantially prevent thebreakage of the dielectric layer 67 and the bottom electrode 66 due to aphysical or chemical impact in a subsequent process, or a conductivelayer may be stacked in order to improve electrical characteristics suchas RC delay.

According to the method for fabricating the semiconductor device inaccordance with the embodiment of the present invention, the ZrHfMOlayer (M is a IV group element) including a mixture of zirconium,hafnium, and a IV group element is formed, where a structure having anequivalent oxide thickness (Tox) of 5 Å±0.5 Å with a dielectric constantof 50 to 60 is obtained. Here, an adequate cell capacitance may beobtained more easily.

Furthermore, the M-rich ZrHfMO layer including a IV group element with arelatively large content is formed at a portion making contact with thebottom electrode or the top electrode, where an increase in leakagecurrent restraining force is obtained.

While the present invention has been described with respect to thespecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

What is claimed is:
 1. A semiconductor device comprising: a dielectriclayer in which zirconium, hafnium, and a N group element are mixed,wherein an equivalent oxide thickness of the dielectric layer is 5 Å±0.5Å.
 2. The semiconductor device of claim 1, wherein the dielectric layerincludes a ZrHfSiO layer or a ZrHfCeO layer.
 3. The semiconductor deviceof claim 1, wherein the dielectric layer has a stack structure of aZrHfMO layer and an M-rich ZrHfMO layer, wherein M is a IV groupelement.
 4. The semiconductor device of claim 1, wherein the dielectriclayer has a triple stacked structure of a first M-rich ZrHfMO layer, aZrHfMO layer, and a second M-rich ZrHfMO layer, wherein M is a IV groupelement.
 5. The semiconductor device of claim 1, wherein the dielectriclayer includes a IV group element having a composition ratio of at least15% or less.
 6. The semiconductor device of claim 1, wherein thedielectric layer has a dielectric constant of 50 to
 60. 7. Thesemiconductor device of claim 3, wherein a thickness of the stackstructure is equal to or less than at least 100 Å.
 8. The semiconductordevice of claim 3, wherein a thickness of the M-rich ZrHfMO layer is 5 Åto 20 Å.
 9. The semiconductor device of claim 3, wherein M-rich ZrHfMOlayer is formed to contact with an electrode of the semiconductordevice.
 10. The semiconductor device of claim 4, wherein a thickness ofthe stack structure is equal to or less than at least 100 Å.
 11. Thesemiconductor device of claim 3, wherein a thickness of the first M-richZrHfMO layer and a thickness of the second M-rich ZrHfMO layer are 5 Åto 20 Å.
 12. The semiconductor device of claim 3, wherein one of thefirst and second M-rich ZrHfMO layers is formed to contact with anelectrode of the semiconductor device.
 13. A semiconductor devicecomprising: a dielectric layer in which zirconium, hafnium, and a IVgroup element are mixed, wherein the dielectric layer includes a ZrHfCeOlayer, wherein the dielectric layer has a dielectric constant of 50 to60.